Synthesis And Properties Of Vegetable Oil-Based Polyurethane Based On CO₂ Conversion

With the increasing demand for polyurethane in people’s daily life,the scale of polyurethane production continues to expand,but traditional polyurethane products have problems of low toxicity,pollution and non-degradation,which are contrary to the concept of green and sustainable development.As constantly increasing for the society’s demand for green,low-carbon,and safety,the development of a synthetic route for the synthesis of biodegradable non-isocyanate polyurethane（NIPU）using vegetable oil as raw material has become one of the current research hotspots.Cottonseed oil is an abundant,cheap and renewable biomass resource in Xinjiang.Therefore,the development of a kind of cottonseed oil-based non-isocyanate polyurethane method has certain social and economic value.In this thesis,cottonseed oil or unsaturated fatty acids were used as starting materials,and vegetable oil-based cyclic carbonates were synthesized through epoxidation and cycloaddition with carbon dioxide（CO₂）.Then polymerization of vegetable oil-based cyclic carbonates with tris（2-aminoethyl）amine was occurred to prepare a biodegradable network cross-linked vegetable oil-based non-isocyanate polyurethane.This method reflects the closed-loop chemical development concept of green,low-carbon and sustainable development from the biomass source and CO₂.First,using 10-undecyenoic acid as a raw material,an epoxy group was introduced into the 10-undecynoic acid structure through an epoxidation reaction,which was then underwent a cycloaddition reaction with CO₂to generate the corresponding cyclic carbonate.The cyclic carbonate reacts with tris（2-aminoethyl）amine to prepare 10-undecyenoic acid-based non-isocyanate polyurethane.The tensile strength of the polyurethane material is 6.07 MPa,the elongation at break is 328%,the glass transition temperature is-3.5℃,the initial thermal degradation temperature is 198℃,and the thermal stability is good.These results suggested that the polyurethane material has a certain application prospect.The tensile strength of the thiol-modified polyurethane is 6.0 MPa,the glass transition temperature is 43℃,and the initial thermal degradation temperature is 183℃.Compared with the unmodified polyurethane,the modified polyurethane has high regularity,the glass transition temperature and the material healing ability are improved,but its thermal stability and crosslinking density are reduced.Compared with the traditional isocyanate synthesis method,this method avoids the use of toxic phosgene and consumes a certain amount of CO₂ greenhouse gas,which provides a new idea and method for the synthesis of non-isocyanate polyurethane.In the previous chapter,the mechanical properties and thermal stability of 10-undecyenoic acid-based polyurethane without alkyl side chains were investigated.In order to further investigate the effect of alkyl side chains on the properties of polyurethane,vegetable oil-based polyurethanes with multiple alkyl side chains were synthesized,mainly focusing on oleic acid with double bonds inside.The oleic acid-based polyurethane and the mercapto-modified oleic acid-based polyurethane were synthesized respectively.Compared with the 10-undecylenic acid-based polyurethane synthesized in the above part,the obtained oleic acid-based polyurethane showed a sharp decrease in tensile strength,but a higher elongation at break（411%）and a larger cross-linking density（1322 mol/m³）.Compared with the thiol-modified 10-undecylenic acid polyurethane,the thiol-modified oleic acid-based polyurethane has better healing ability and elongation at break,but its glass transition temperature is lower（-25℃）.Therefore,this type of oleic acid-based polyurethane material has higher thermal stability and healing ability,and could applied to different fields in combination with the 10-undecylenic acid polyurethane material,providing a wider application space for vegetable oil-based polyurethane.Finally,in order to avoid the purification step of the unsaturated fatty acid ester,and cottonseed oil is used as the raw material to react with tris（2-aminoethyl）amine to obtain a more atom-economic polyurethane material.This polyurethane material has an extremely high crosslinking density（2645 mol/m³）,which improves the glass transition temperature（68℃）and thermal stability of the material.In addition,Cottonseed oil polyurethane raw materials come from a wide range of sources and have more economic value,which is in line with the concept of carbon neutrality.To sum up,the polyurethane synthesis method adopted in this chapter provides a reference for the industrial production of vegetable oil-based polyurethane.